It is well known that, as a new generation of green illuminating light source, LED has many advantages such as high luminous efficiency, long lifetime, vivid colour, energy-saving, environment-protecting and the like, and it has more and more extensive application fields such as indoor and outdoor illuminating, backlight source, medical field, transportation, plant growth and so on.
An LED chip is an critical component of the LED, and there are two paths to improve the luminous efficiency of LED products, one is improving the photo-electricity parameters of the LED chip and the other is developing new technologies of coating phosphor powder, wherein the photo-electricity parameters of LED chip products are improved mostly by chip manufacturers, and the new technologies of coating phosphor powder are developed continuously by packaging plants.
In prior art, the process of coating phosphor powder in LED manufacturing includes such packaging modes as phosphor powder being far away from the chip, phosphor powder uniformly distributed in packaging material and phosphor powder attached tightly to the chip surface. The packaging mode of phosphor powder uniformly distributed in packaging material among others is easy to be performed, but in this mode the phosphor powder has low excitation efficiency. The mode of phosphor powder being far away from the chip has not been yet industrially produced due to its complex and uncontrollable process. The mode of phosphor powder attached tightly to the chip surface is achieved by bonding the phosphor powder to the chip by means of intermediate packaging material, the defect of which is the refractive index of the intermediate package material is low, therefore the light emitted by the chip is easy to be totally reflected, which results in heat accumulating and reduces the light extraction efficiency of the chip and affects excitation of the phosphor powder (the excitation temperature of the phosphor powder is relatively high). Coating phosphor powder directly on the semi-finished products which has been die attached and wire bound may waste a number of phosphor powder.